Siren intermediaLesser Siren

Geographic Range

Siren intermedia, the Lesser Siren, ranges from the Coastal Plains of Virginia to Florida, then westward to southern Texas and northeastern Mexico. Populations extend northward in the Mississippi Valley to Illinois, Indiana, and southwestern Michigan. Geographic isolates occur in northern Indiana, southwest Michigan, northeastern North Carolina, and southeastern Virginia.(Petranka 1998) This range is occupied by three subspecies, they are S. i. intermedia, S. i. nettingi, and S. i. texana. All of these subspecies only vary slightly in physical characteristics such as length and color (Conant and Collins, 1998).

Habitat

Siren intermedia will inhabit most any slow and sluggish body of water that is shallow and with plenty of aquatic vegetation, including marshes, ponds, ditches, and canals. In most circumstances they need a permanent or semi-permanent body of water but they are able to move short distances over land if factors are right or stay encased in a cocoon of slime if drought occurs. (Conant and Collins, 1998 (Expanded 3rd Ed.); Harding, 1997)

  • Aquatic Biomes
  • lakes and ponds

Physical Description

Siren intermedia is an eel-like salamander with a long slender body (18-68 cm long) and a very small dorsal fin that runs from the vent to the tail tip. It has only a pair of front legs; each foot has four toes. The front legs are very reduced and the rear legs are completely absent. The head is rather flattened, and there are bushy external gills located on each side of the head. Siren intermedia varies in coloration from light grayish green to olive or black; there are also small irregular markings (dots) that are visible on lighter colored individuals.

Larvae and juveniles are more brightly marked, with a red band across the nose and along the side of the head. (Conant and Collins, 1998 (Expanded 3rd Ed.); Harding, 1997; Petranka, 1998)

Development

Reproduction

The courtship behavior of Siren intermedia has not yet been described. Fertilization has been presumed to be external, since the females lack cloacal sperm storage areas. There is thought to be a lot of aggression during mating due to the amount of scaring from bite marks on both the males and females. Eggs are laid in early spring they are deposited in shallow depressions in the soft bottom of the occupied water body, usually in highly vegetated areas. In these shallow depressions the female will lay from 12 to over 300 eggs; the female may lay multiple clutches through out the season. Freshly laid eggs are dark brown and 2.5-3 mm in diameter. The hatchling larvae are about 1.1 cm in length. (Petranka 1998; Harding 1997) (Conant and Collins, 1998 (Expanded 3rd Ed.); Harding, 1997; Petranka, 1998)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • Average number of offspring
    200
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    730 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    730 days
    AnAge

Lifespan/Longevity

Behavior

Siren intermedia is a nocturnal species, which may minimize predation risks from diurnal predators such as fish and wading birds.(Petranka 1998) It spends the daylight period hidden in debris on the bottom of bodies of shallow water or burrowed in the mud and vegetation. In the case that the water dries up, Siren intermedia will burrow into the mud were it can survive for months. In this situation the siren's skin glands will secrete a substance that will dry and form a cocoon over the body (except for the mouth), protecting the siren from drying up until the water returns.

Siren intermedia is very vocal, which is unusual for a salamander. It communicates with clicks when other sirens are around and when disturbed or attacked by a predator it will emit a very shrill call (Harding 1997).

Food Habits

Siren intermedia feeds primarily on aquatic invertebrates such as crustaceans, insect larvae, worms, and snails. They will also readily consume young amphibian larvae and their own eggs. Siren intermedia often feeds by gulping large quantities of material at a time, which is filtered through the bronchial openings. Vegetable matter sometimes found in their digestive tracts is probably eaten accidentally.

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • aquatic crustaceans

Economic Importance for Humans: Positive

Sirens are occasionally used for fish bait, but this species normally attracts little attention from humans. They occupy a predatory niche in shallow freshwater habitats, and have ecological value in the environment.

Economic Importance for Humans: Negative

On occasion a Siren might take a fisherman's baited hook, but this would be an uncommon and minor annoyance. These animals are properly considered harmless to human interests.

Conservation Status

Siren intermedia is extremely rare and possibly extirpated in Michigan but this species is not threatened over most of its range. It could be harmed by chemicals such as Rotenone, which is used as a fisheries management tool and can be fatal to aquatic amphibians such as Siren intermedia. Another factor that may affect the vitality of this species is habitat destruction and the filling in of wetlands.

Contributors

Jesse Gabbard (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

References

Cogger, H., R. Zweifel. 1998, 2nd Ed.. Encyclopedia of Reptiles and Amphibians. San Diego, CA: Academic Press.

Conant, R., J. Collins. 1998 (Expanded 3rd Ed.). A Field Guide to Reptiles and Amphibians of Eastern and Central North America. New York, NY: Houghton Mifflin Company.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor: The University of Michigan Press.

Petranka, J. 1998. Salamanders of the United States and Canada. Washington D.C.: Smithsonian Institution Press.